/*
 * Created on Jul 18, 2004
 * Created by Alon Rohter
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

package com.aelitis.azureus.core.peermanager.utils;

import java.util.ArrayList;

import org.gudy.azureus2.core3.util.AEMonitor;

import com.aelitis.azureus.core.networkmanager.OutgoingMessageQueue;
import com.aelitis.azureus.core.peermanager.messaging.Message;
import com.aelitis.azureus.core.peermanager.messaging.azureus.AZHave;
import com.aelitis.azureus.core.peermanager.messaging.azureus.AZMessage;
import com.aelitis.azureus.core.peermanager.messaging.bittorrent.BTHave;
import com.aelitis.azureus.core.peermanager.messaging.bittorrent.BTMessage;
import com.aelitis.azureus.core.peermanager.messaging.bittorrent.BTMessageFactory;

/**
 * Utility class to enable write aggregation of BT Have messages, in order to save bandwidth by not wasting a whole network packet on a single small
 * 9-byte message, and instead pad them onto other messages.
 */
public class OutgoingBTHaveMessageAggregator {

    private final ArrayList pending_haves = new ArrayList();
    private final AEMonitor pending_haves_mon = new AEMonitor("OutgoingBTHaveMessageAggregator:PH");

    private byte bt_have_version;
    private byte az_have_version;

    private boolean destroyed = false;

    private final OutgoingMessageQueue outgoing_message_q;

    private final OutgoingMessageQueue.MessageQueueListener added_message_listener = new OutgoingMessageQueue.MessageQueueListener() {
        public boolean messageAdded(Message message) {
            return true;
        }

        public void messageQueued(Message message) {
            // if another message is going to be sent anyway, add our haves as well

            String message_id = message.getID();

            if (!(message_id.equals(BTMessage.ID_BT_HAVE) || message_id.equals(AZMessage.ID_AZ_HAVE))) {
                sendPendingHaves();
            }
        }

        public void messageRemoved(Message message) {/* nothing */
        }

        public void messageSent(Message message) {/* nothing */
        }

        public void protocolBytesSent(int byte_count) {/* ignore */
        }

        public void dataBytesSent(int byte_count) {/* ignore */
        }

        public void flush() {
        }
    };

    /**
     * Create a new aggregator, which will send messages out the given queue.
     * 
     * @param outgoing_message_q
     */
    public OutgoingBTHaveMessageAggregator(OutgoingMessageQueue outgoing_message_q, byte _bt_have_version, byte _az_have_version) {
        this.outgoing_message_q = outgoing_message_q;
        bt_have_version = _bt_have_version;
        az_have_version = _az_have_version;

        outgoing_message_q.registerQueueListener(added_message_listener);
    }

    public void setHaveVersion(byte bt_version, byte az_version) {
        bt_have_version = bt_version;
        az_have_version = az_version;
    }

    /**
     * Queue a new have message for aggregated sending.
     * 
     * @param piece_number
     *            of the have message
     * @param force
     *            if true, send this and any other pending haves right away
     */
    public void queueHaveMessage(int piece_number, boolean force) {
        if (destroyed)
            return;

        try {
            pending_haves_mon.enter();

            pending_haves.add(new Integer(piece_number));
            if (force) {
                sendPendingHaves();
            } else {
                int pending_bytes = pending_haves.size() * 9;
                if (pending_bytes >= outgoing_message_q.getMssSize()) {
                    // System.out.println("enough pending haves for a full packet!");
                    // there's enough pending bytes to fill a packet payload
                    sendPendingHaves();
                }
            }
        } finally {

            pending_haves_mon.exit();
        }
    }

    /**
     * Destroy the aggregator, along with any pending messages.
     */
    public void destroy() {
        try {
            pending_haves_mon.enter();

            pending_haves.clear();
            destroyed = true;
        } finally {
            pending_haves_mon.exit();
        }
    }

    /**
     * Force send of any aggregated/pending have messages.
     */
    public void forceSendOfPending() {
        sendPendingHaves();
    }

    /**
     * Are there Haves messages pending?
     * 
     * @return true if there are any unsent haves, false otherwise
     */
    public boolean hasPending() {
        return !pending_haves.isEmpty();
    }

    private void sendPendingHaves() {
        if (destroyed) {

            return;
        }

        try {
            pending_haves_mon.enter();

            int num_haves = pending_haves.size();

            if (num_haves == 0) {

                return;
            }

            // single have -> use BT

            if (num_haves == 1 || az_have_version < BTMessageFactory.MESSAGE_VERSION_SUPPORTS_PADDING) {

                for (int i = 0; i < num_haves; i++) {

                    Integer piece_num = (Integer) pending_haves.get(i);

                    outgoing_message_q.addMessage(new BTHave(piece_num.intValue(), bt_have_version), true);
                }
            } else {

                int[] piece_numbers = new int[num_haves];

                for (int i = 0; i < num_haves; i++) {

                    piece_numbers[i] = ((Integer) pending_haves.get(i)).intValue();
                }

                outgoing_message_q.addMessage(new AZHave(piece_numbers, az_have_version), true);

            }

            outgoing_message_q.doListenerNotifications();

            pending_haves.clear();

        } finally {

            pending_haves_mon.exit();
        }
    }

}
